Bats

There are a dozen or so species of bats that can be found in the UK with a few more species that are extremely rare which have only been seen a few times. As most people know bats echo locate their prey in flight using very high pitched sound pulses which are above the hearing range of most people, particularly us older folks. However, there is technology around to help out with this. Bat detectors reduce the frequency of the bat calls down by a factor of 10 into the human hearing range, they are typically the size of a mobile phone and are simply pointed in the general direction of the bat and the bat calls are played through a small loud speaker. These calls can also be recorded using a small tape recorder which than be replayed through some specialist computer software. When a bat is out hunting it sends out short sound pulses and listens for an echo from an air-borne insect. Once the bat has detected an insect it closes in and increases the rate of transmitted pulses. The top picture on the right shows a recording we made over the village pond of a Daubenton’s bat and you can see how the sound pulses become closer together until the moth meets it’s demise in a final blur of sound. Click here to hear a recording of Common and Soprano Pipistrelles and Daubentons all flying at the same time over the pond.
Most bats use different sound pulses which are analysed on the computer to aid species identification. Some examples are shown in the other pictures on the right.
The group has purchased two sets of detectors and recorders and has started to carry out surveys around the village. We have been helped enormously by a specialist from Bristol University employed by Wessex Water to survey their site. We have already identified seven species around the village in the brief period we have been surveying.
The equipment is very easy to use and we are more than happy to lend it with some training to people in the village who would like to find out what is flying around their garden. For more information contact Dave Emery.